/Engine/Source/Editor/MovieSceneTools/Public/TrackEditors/SubTrackEditor.h
Find or create a sub track. If the given track is a subtrack, it will be returned.
[UMovieSceneSubTrack](API\Runtime\MovieScene\Tracks\UMovieSceneSubTrack) * FindOrCreateSubTrack ( [UMovieScene](API\Runtime\MovieScene\UMovieScene) * MovieScene, [UMovieSceneTrack](API\Runtime\MovieScene\UMovieSceneTrack) * Track ) const